For the purpose of obtaining three-dimensional ultrasonic diagnostic image of human superficial tissues as described above conveniently and within short time, it is necessary to have a wide visual field by an array type element near the surface of human body and mechanical scanning along the shape of human body surface in a direction perpendicularly crossing the scanning direction of the array type element. However, a hand-carried ultrasonic probe has such advantages that three-dimensional images of all types of superficial tissues are obtained by a single three-dimensional ultrasonic probe, and troublesome procedure during diagnosis to exchange the probe can be eliminated and there is no need to use a plurality of three-dimensional ultrasonic probes, and it is very advantageous from the viewpoint of cost. On the other hand, in the ultrasonic probe to obtain three-dimensional tomograms of the regions such as carotid arteries, thyroid gland, etc., the size of the probe must be made as small as possible because of the site of human body to be diagnosed under chin. Thus, there are demands, which contradict against each other, i.e. the necessity to have wider three-dimensional diagnostic region and the realization of the demands to have smaller type of three-dimensional ultrasonic probe. Because it is a hand-carried ultrasonic probe, the probe must be in small size and light in weight.
The present invention provides the means to solve the problems, i.e. the problem of small size and lightweight design to have wider diagnostic region and the probe in smaller size, and the problem to ensure adherence to or close contact with the part of human body, which is relatively flat.
As a conventional method to acquire tomograms of superficial human tissues, the Patent Document 1 as given below discloses means for obtaining tomographic image of the entire mamma (breast), which uses an applicator for breast on the ultrasonic probe, and the tomographic image of the entire region of mamma is obtained by rotating the probe itself.
However, the invention disclosed in the Patent-Document 1 describes an apparatus to be exclusively used for the diagnosis of mammary gland by rotating the existing array type ultrasonic probe. Doctors cannot operate it by directly gripping the probe in the same manner as the case of the hand-carried ultrasonic probe. In addition, other diagnostic regions such as carotid arteries, thyroid gland, etc. cannot be diagnosed by a single three-dimensional ultrasonic probe.
The Patent-Document 2 as given below describes the means to obtain tomographic image of the entire mamma by arranging the ultrasonic probe in water tank and by moving the probe in parallel direction. Also, the Patent Document 3 as given below describes means for acquiring ultrasonic image by moving the ultrasonic probe in parallel direction by using belt or the like.
However, similarly to the case of the Patent Document 1, the Patent Document 2 does not describe a hand-carried three-dimensional ultrasonic probe. The apparatus itself is in large scale and troublesome procedures are required in the preparation in advance. Also, diagnosis cannot be conveniently made on other diagnostic regions such as carotid arteries, thyroid gland, etc. Further, by applying the embodiment of the Patent Document 3, a mechanism to move the ultrasonic element in parallel direction by means of a wire 31 can be used to estimate the use of the hand-carried ultrasonic probe as shown in FIG. 20. However, when the array type element 30 is moved in parallel by using wire, timing belt, etc., a pulley 32 must be used to drive the wire 31 or the like on both ends of the element to be moved. Therefore, when the structure of this type is used, as shown in FIG. 21, moving range must be restricted, and this gives restriction on the width of the element 30 or on the diameter of the pulley 32, and wide contact region of human body is required, which is wider than the mechanical moving range, and this cannot be applied in case of the hand-carried three-dimensional ultrasonic probe. In particular, when diagnosis must be made on carotid arteries, thyroid gland, etc., the hand-carried three-dimensional ultrasonic probe has such problems that chin and other region of human body may hinder the application of the hand-carried three-dimensional ultrasonic probe. FIG. 20 and FIG. 21 each represents a case where the ultrasonic element 30 is mounted so that it can be moved in parallel by using a slide bearing 33, and the ultrasonic element is moved in parallel by rotary movement of the motor 34 and by a transmission mechanism using the pulley 32 and the wire 31.
The Patent Document 4 as given below describes the means to use the hand-carried three-dimensional ultrasonic probe by rotating around one end of the array type element in electronic scanning direction as the center.
However, when the means to acquire three-dimensional ultrasonic image is used, in which one end in electronic scanning direction of the array type element is rotated around it as in the case of the invention of the Patent Document 4, rotary momentum of a part away from the center of rotation is increased more compared with the rotation momentum near the center of the mechanical rotation. As a result, the pitch of two-dimensional cross-sectional area, which serves as the original data to build up the three-dimensional tomographic image, is finer in the region nearer to the rotation center, and the pitch is rougher as it goes away from the rotation center. In proportion to the distance from the rotation center, the pitch of the slice cross-section of the two-dimensional cross-sectional surface is turned to be rougher. Thus, when three-dimensional image is built up by using the cross-sectional image data at a position away from the rotation center, resolution will be rougher at the site away from the rotation center. Further, because, in the electronic scanning, the array type element is rotating around the end portion as the center, a mechanism is needed, which has the rotation center axis at a position away from the length of the element of the electron scanning direction of the array type element. When it is necessary to diagnose the site such as carotid arteries, thyroid gland, etc., the human body contacting region, which is larger than the length of the element, touches the region of chin, and it is difficult to have the ultrasonic probe properly at a position as desired.
In the three-dimensional ultrasonic probe as described in the Patent Document 5, description is given on the means, by which the hand-carried three-dimensional ultrasonic probe can be used by obtaining three-directional ultrasonic tomographic image through mechanical swinging of a convex type array element.
However, in the three-dimensional ultrasonic probe as described in the Patent Document 5, the curvature of the tip of the probe, which comes into contact with the aimed site of human body, is determined, depending on the distance from the swinging rotation center of the element to the tip of the array type element because three-dimensional ultrasonic tomographic image can be obtained by mechanically swinging the convex type array element. In case it is necessary to bring the probe into contact with the site of the tissue, which is relatively flat, i.e. in order to have human body to be contacted by two ends through mechanical swinging scanning, it is necessary to have longer distance from the rotation center of mechanical swinging to the tip of the array type element and to increase the curvature of the human body contact region. However, in order to increase the distance from the rotation center of the mechanical swinging to the tip of the array type element, the entire size of the hand-carried three-dimensional ultrasonic probe must be larger, and the increase of the size and the weight of the hand-carried three-dimensional ultrasonic probe causes such problems that the probe is difficult to handle for the purpose of diagnosis.